1 . Field
The advantageous embodiments described herein relate to closed and semi-closed containers that receive internal or external pressure. More particularly, the advantageous embodiments described herein relate to ducts and methods of making duct systems, and still more particularly, toward duct systems used in aerospace vessels, such as aerospace vessels, helicopters, rockets, space vessels, and others.
2 . Background
Modern aerospace vessels contain numerous ducts of various forms to create a safe environment for people, animals, and equipment in hostile environments found in and around aerospace vessels. For example, in a typical midsize passenger airplane over 500 duct variants can be found. Ducts are used to provide cabin air conditioning, cockpit cooling, ram air cargo heating, water separation, avionic cooling, deicing, air trim, auxiliary power, recirculation systems, exhaust systems, and positive pressure in the cabin to deter the entry of smoke from a cargo fire. Thus, the environmental control duct system of an airplane is complex and adds significant weight to an airplane. Economizing weight is always of great concern to airplane designers because a single pound can impact the value of an aerospace vessel significantly. The weight of the aerospace vessel is important because heavier aerospace vessel intrinsically require more fuel and can carry fewer passengers or cargo relative to lighter aerospace vessel of the same design. These same concerns exist with respect to nearly all aerospace vessels to a greater or lesser degree.
The processes and materials for conventional duct manufacturing and assembly can be expensive and possibly ineffective. Conventional ducts, such as metallic ducts, are heavy, costly to tool and fabricate, assemble, maintain, and have difficulty meeting stringent requirements, such as Federal Aviation Administration requirements.
Plastic ducts are used in an environmental control system of an aerospace vessel. However, plastic ducts also have disadvantages in some cases, such as geometry limitations, the potential requirement for flanges for bonding, inconsistent wall thicknesses, weight, and solvent stress factors.
Ducts made of reinforced composite materials are also used in an environmental control system of an aerospace vessel. However, reinforced composites also have several disadvantages. For example, many composites transmit noise and require expensive materials and tools, as well as a great deal of time and labor to process. Composites are also subject to micro damage when handled and stricter alignment tolerances.